§ 112, 113. THE GULF STREAM. 37 



they reached the middle of the stream. We rarely hear of planks, 

 or wrecks, or of any floating substance which is cast into the sea 

 on the other side of the Gulf Stream being found along the coast 

 of the United States. Drift-wood, trees, and seeds from the West 

 India islands, are often cast up on the shores of Europe, but rare- 

 ly on the Atlantic shores of this country. 



112. We are treating now of the effects of physical causes. The 

 -vvhy so sloughed ofif. qucstiou to wMch I ask attention is, Why does the 

 Gulf Stream slough off and cast upon its outer edge, sea-weed, 

 drift-wood, and all other solid bodies that are found floating upon 

 it ? One cause has been shown to be in its roof-shaped current ; 

 but there is another which tends to produce the same effect ; and 

 because it is a physical agent, it should not, in a treatise of this 

 kind, be overlooked, be its action never so slight. I allude now 

 to the effects produced upon the drift matter of the stream by the 

 diurnal rotation of the earth. 



113. Take, for illustration, a railroad that lies north and south 

 niustration. in our hemisphere. It is well known to engineers 



that when the cars are going north on such a road, their tendency 

 is to run off on the east side ; but when the train is going south, 

 their tendency is to run off on the west side of the track — i. e., 

 always on the right-hand side. Whether the road be one mile or 

 one hundred miles in length, the effect of diurnal rotation is the 

 same ; and, whether the road be long or short, the tendency to 

 run off, as you cross a given parallel at a stated rate of speed, is 

 the same ; for the tendency to fly off the track is in proportion to 

 the speed of the train, and not at all in proportion to the length 

 of the road. Now, vis inertioe and velocity being taken into the 

 account, the tendency to obey the force of this diurnul rotation, and 

 to trend to the right, is proportionably as great in the case of a 

 patch of sea- weed as it drifts along the Gulf Stream, as it is in the 

 case of the train of cars as they speed to the north along the iron 

 track of the Hudson River railway, or any other railway that lies 

 north and south. The rails restrain the cars and prevent them 

 from flying off; but there are no rails to restrain the sea- weed, 

 and nothing to prevent the drift-matter of the Gulf Stream from 

 going off in obedience to this force. The slightest impulse tend- 

 ing to turn aside bodies moving freely in water is immediately 

 felt and implicitly obeyed. 



